Oxygen concentrator



FIG. 1 is a right side perspective view of an oxygen concentrator showing my new design;

FIG. 2 is a left side perspective view thereof;

FIG. 3 is a left side elevational view thereof;

FIG. 4 is a front elevational view thereof;

FIG. 5 is a right side elevational view thereof;

FIG. 6 is a rear elevational view thereof; and

FIG. 7 is a top plan view thereof.

The broken line showing of a cord and plug is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for an oxygen concentrator, as shown and described. 